When light travels from one medium to another, some portion of the light is reflected from the interface between the two media. For example, typically about 4-5% of the light shining on a clear plastic substrate is reflected at the top surface.
The back lighting for mobile hand held and laptop devices are not effective to provide desired display quality in the presence of the reflection of the external lighting from the top surface and internal interfaces of the display devices, which in turn reduces contrast ratio and can downgrade viewing quality from the interfering image of external objects.
Different approaches have been employed to reduce the reflection of the top surface of display devices. One approach is to use antireflective coatings such as multilayer reflective coatings consisting of transparent thin film structures with alternating layers of contrasting refractive index to reduce reflection. However, it can be difficult to achieve broadband antireflection using the multilayer antireflective coating technology.
Another approach involves using subwavelength surface structure (e.g. subwavelength scale surface gratings) for broadband antireflection, wherein the phrase subwavelength is used to describe an object or structure having one or more dimensions smaller than the length of the wave with which the object or structure interacts. For suppression of Fresnel reflections from optical surfaces, subwavelength structured features lead to continuous-profile surface-relief grating as an effective medium to minimize reflection for a range of wavelengths greater than the subwavelength structured features on the surface. Methods for creating the subwavelength surface structure (e.g., by lithography) tend to be relatively complicated and expensive. Additionally, it can be challenging to obtain durable antireflection surfaces from the subwavelength scale surface gratings for front surface applications.
Antireflective and antiglare solutions had been developed to reduce the specular reflection of display devices. However, the hybrid antireflective antiglare surface has a structural dimension close to the wavelengths of the visible light spectrum and therefore can induce higher haze (i.e. >4%) to reduce display quality.